EA018034B1 - Method for abrasion resistant white cast chromic iron smelting for production of wearing parts - Google Patents

Abstract

The invention relates to the methods for the abrasion-resistant cast chromic iron smelting and can be used to produce the wearing parts, including the grinding media. The invention provides a method for the white chromic iron production with the defined high content of chromium under conditions of the continuous smelting in the duplex process of the iron having various chromium content, comprising charge cupola melting to give the liquid iron with the subsequent storage and finishing as to chemical specifications of the liquid iron in the mixer. At the first stage in the method the iron is smelted using the initial charge and is added based on the total content of the mixer into the present in the mixer iron rest having the chromium content, different from defined and optionally correct the iron content as to C, Si, Mn to give the white chromic iron with the defined high content of chromium, the chromium content in the initial charge being chosen based on achievement of the defined value of the chromium content while mixing in the defined ratio of the liquid iron produced from the initial charge with the present in the mixer iron rest. At the second stage, after storage of the return of the white chromic iron with the defined high content of chromium, the iron is smelted using the constant charge, into which the return of the white chromic iron with the defined high content of chromium is introduced.

Description

The invention relates to metallurgy, in particular to methods of smelting wear-resistant chromium cast iron, and can be used to obtain wearing parts, including grinding media (balls, tsilpebs), etc., used in ball mills for grinding various materials in the production of cement, cellular concrete, mineral processing, for the preparation of coal-fired pulverized fuel, in the chemical and metallurgical industries.

Practice has shown that at this stage, the organization of mass production of grinding media is most appropriate using automatic molding lines (AFL) of the Disamatic type, equipped with induction channel mixers (hereinafter referred to as the mixer) with devices for automatic filling of molds operating in duplex with induction furnaces or cupolas.

However, when using the duplex process of cupola-mixer, it is possible to melt only cast iron with a limited chemical composition with a limited content (0.07-0.2%) of chromium or to melt only alloyed, including chromium, cast iron. At the same time, in industrial practice, often along with cast irons of traditional composition with limited chromium content from the same mixer, sequential production of, for example, a certain amount of white chromium cast iron is required, and then again cast iron with limited chromium content. But due to the presence in the mixer of the remainder of the metal of the previous melting, the so-called swamps, for example, of white low-chromium cast iron, the transition to white cast iron with a high content of chromium, and then the transition to gray cast iron is a difficult technological task.

From the successful solution of such a technological problem, i.e. for producing white cast iron with a chromium content of more than 0.5% under conditions of continuous smelting in the duplex process, in particular, the possibility of efficient organization of mass production of grinding media depends.

A study of the current level of technology has shown that technical and more so patent information on this issue is missing or extremely limited.

So, there is a known method of producing cast billets from white wear-resistant cast iron for wear parts, including smelting, alloying and modifying cast iron to produce cast iron of a given chemical composition, producing castings by casting cast iron into sand or metal molds, cleaning and heat treatment of castings [1]. In this case, cast iron of the following composition is used, wt. %: carbon 2.4-4.0; silicon 0.5-1.5; manganese 2-4; nickel 2-4; chrome 8-12; molybdenum 0.5-8.0; boron 0.10.3; barium 0.005-0.001; phosphorus 0.02-0.07; sulfur 0.02-0.07; iron is the rest.

The disadvantage of this method is the use of an increased number of expensive and scarce alloying elements: chromium, nickel, molybdenum and others, which significantly increases the cost of castings and makes it often incommensurable with an increase in the operational stability of grinding media. In addition, such cast iron cannot be smelted in a cupola, but only in an electric furnace, which limits its wider use.

Also known is a method of producing castings of wearing parts from white wear-resistant cast iron [2], in which a naturally-alloyed material containing impurities Cr, Τι, V, Mo, Cu, A1, etc. is used as an alloying alloy. Since this alloying additive contains 8-12 % silicon, its addition to cast iron is limited to 6%. A further increase in this additive leads to an increase in the silicon content in cast iron, the appearance of a half-structure - satser, and a decrease in hardness. Thus, the total content of alloying elements in cast iron is insignificant (the maximum chromium content is 0.2%), and the guaranteed white structure and hardness are obtained by controlling the degree of supercooling by changing the content of C and 8ί [3].

The transition from white cast iron to gray using a mixer is not difficult and is carried out by simple adjustment of the chemical composition according to C and 8ί and modification.

When using this method of producing white cast iron, the hardness of castings of grinding media with a diameter of 20-30 mm is achieved in the range of 380-415 HB.

The prototype of the proposed method in the prior art is not identified.

Thus, the objective of the invention is to develop a method for producing white chromium cast iron with a given high chromium content under conditions of continuous smelting in a duplex process of cast iron with different chromium contents. In particular, the method should provide the smelting of white chrome cast iron with a chromium content of 0.5-2% for castings of grinding media with a diameter of 30-60 mm with a guaranteed hardness of at least 415 HB and with the necessary limits for the chromium content in the mixer when switching to white cast iron (up to 0.07% Cg) and gray cast iron (up to 0.2% Cg).

The problem is solved by the claimed method of producing white chromium cast iron with a given high chromium content under conditions of continuous casting in a duplex process of cast iron with various chromium contents, including melting the charge in a cupola with production of molten cast iron with subsequent accumulation and finishing of molten cast iron by chemical composition in the mixer, in the first stage, cast iron is smelted using the starting charge and added to the total volume of the mixer in the remainder of the cast iron in the mixer with the content m of chromium other than specified, and, if necessary, adjust the composition of cast iron according to C, δί, Mp to obtain white chromium cast iron with a given high chromium content, and the chromium content in the starting charge is selected in order to achieve a specified value of chromium content when mixed in a given proportions by

- 1 018034 liquid iron cast from the starting mixture with the remainder of the iron in the mixer, and in the second stage, after accumulating the return of white chrome cast iron with a given high chromium content, the cast iron is smelted using a constant charge, which contains the return of white chrome cast iron with a predetermined high chromium content.

Thus, in fact, the residue in the mixer is white cast iron with a chromium content of 0.07%, always remaining after the previous heat, the so-called the swamp is diluted with cast iron melted in a cupola using the starting mixture with the estimated amount of chromium, moreover, the addition of such cast iron is carried out in the mixer to its full volume, after which chrome cast iron is poured into molds until a sufficient amount of chromium cast iron is accumulated, after which the starting batch is canceled, the composition of cast iron is adjusted according to C, δί, Mn and Cr taking into account the return of chromium cast iron, it is poured into a mixer with subsequent pouring into molds until the end of the company smelting chrome cast iron guna, after which the remainder of the chrome cast iron in the mixer (swamp) is diluted with cast iron smelted for a gray cast iron containing, for example, foundry pig iron, and returning gray cast iron to fill the mixer and bringing the chromium content to a minimum amount (up to 0.2% ) when pouring forms of gray cast iron. The described process can be repeated at any necessary time any necessary number of times. At the same time, in a simple and unexpected way, the authors managed to solve the problem of producing chromium cast iron without disrupting the melting of traditional low-chromium grades of cast iron, i.e. with the transition from white cast iron to white chromium and from white chromium to gray with the necessary limits for low chromium content.

In preferred embodiments of the invention, scrap B10 of corrosion-resistant and heat-resistant chromium steels with Cr content of 16-18%, Τι - not more than 0.8%, N1 - not more than 0.6% is introduced into the starting charge.

In the most preferred forms of implementation, as a starting charge, a charge of the following composition is used, wt.%:

pig iron L6 14-16 return fittings 64-66 steel scrap A1 14-16 steel scrap B10 4-6.

Moreover, as the constant charge is preferably used a mixture of the following composition, wt.%:

pig iron L411-13 white return of chromium cast iron 49-51 pig iron scrap 19-21 steel scrap 1A 14 - 16 steel scrap B102-4.

Castings of white chrome cast iron obtained by the claimed method have a guaranteed hardness of at least 415 HB. Thus, the subject of the invention is the use of white chrome cast iron, obtained by the claimed and described above method, for the manufacture of wearing parts, in particular grinding media.

Below, the advantages and advantages of the proposed method will be discussed in more detail on one of the preferred implementation examples, which should be considered only as an illustration, but not limitation. Moreover, it will be clear to a person skilled in the art that various variations are possible, in particular, in terms of the qualitative and quantitative composition of the starting and constant charge, etc.

Example.

Was established the following chemical composition of melted chromium cast iron, wt.%: C 2,63,2; δί to 1.3; MP 0.5-1.0; Cr 0.5-2.0. The hardness of castings is 415-530 HB.

Cast iron was smelted in a cupola 0 = 6 t / h with a stationary piggy bank.

Smelting of white chrome cast iron was carried out under real production conditions, when it became necessary to melt it after smelting ordinary white cast iron intended to be obtained by annealing castings from malleable cast iron, followed by a transition from white chrome cast iron to gray.

3 hours before the end of smelting of white cast iron, the charge in the cupola was adjusted to obtain C 3.2-3.3% and δί 1.2-1.4%. The charge filling in the cupola was stopped, the remainder of the iron was poured into the mixer. The residual amount of cast iron (swamp) in the mixer should be minimal and not exceed 1.2-1.8 tons (2-3 buckets with a capacity of 600 kg).

In the changeover, instead of models for castings from white cast iron, cast models were installed on the molding

- 2 018034 wok grinding media.

The transition from white to white chrome cast iron was carried out in accordance with the following instructions:

For the initial launch of the production of white chrome cast iron (i.e., in the absence of return), load a cupola with the starting charge (see table 1), which includes scrap B10 of corrosion-resistant and heat-resistant chromium steels with a Cr content of 16-18%, Τι - not more than 0.8%, N1 - not more than 0.6% (GOST 2787-75).

Table 1. The calculation of the starting mixture to obtain chromium cast iron

The name of the charge materials and the calculation of additives Number of mater, in charge, kg Content. % Amount in the metal plant, kg Corner kind Silicon Chromium In the material in the charge In the material in the charge IN material in the charge Pig iron L6 fifteen 4.0 0.6 1.38 0.20 • 15x5.5 = 82.5 Return fittings 65 3.10 2.0 1.35 0.87 0,07 0,045 65x5.5 = 357.5 Steel scrap 1A fifteen oh 3 0,045 0.3 0,045 0,07 0.01 15.5x5.5 = 82.5 Steel scrap B10 5 - - - sixteen 0.8 5x5.5 = 27.5 Total in charge one hundred - 2.65 - 1,11 - 0.845 550 Carbon stick (10%) 2.65x0.1 = 0.265 Silicon burnout (15%) 1.11x0.15 = 0.111 Chrome fume (20%) - - - - - - 1) .34. + -: 0.2 ( = 0.169 The content in the mixture, taking into account fumes (poigaoa! 2,915 0.94 0.68

Cast iron should only be started after feeding three buckets (3x0.6 = 1.8 t) of chrome cast iron to the mixer to dilute and average the residue (swamp) (the total mass of the metal in the mixer is about 3.5 t);

approximate chemical composition of the remainder of white cast iron in the mixer, wt.%: C = 3.1; 81 = 1.35; Cr = 0.07;

the calculated chemical composition of chromium cast iron supplied to the mixer to dilute the metal residue, wt.%: C - 2.9; 81-0.94; Cr - 0.68.

We take, for example, that the remainder of the metal in the mixer is 1.8 tons, i.e. 3 buckets. Then the average chemical composition of cast iron after dilution will be as follows, wt.%:

With _cf = 3x3.1 + 3x2.9 = 18.0: 6 = 3.0;

8ύ _ρ = 3 x 1.35 + 3 x 0.94 = 7.8: 6 = 1.15;

SGSr = 3 x 0.07 + 3 x 0.68 = 2.250: 6 = 0.375

To obtain a given chemical composition of cast iron using the accumulated return of chromium cast iron, the starting charge was canceled and replaced with a constant charge.

The calculation of the charge for grinding bodies, taking into account the use of return of chrome cast iron, is given in table. 2.

- 3 018034

Table 2. Calculation of the mixture, taking into account the use of return of chrome cast iron

The name of the charge materials and the calculation of additives Number of mater, in charge, kg Content% Amount in the metal plant, kg Corner ROD Silicon Chromium In the material in the charge IN material in the charge in the material in the charge Pig iron L4 12 4.0 0.48 1.38 0.166 • - 12x5.5-6.6 Cast Iron Return fifty 2.9 1.45 0.94 0.47 0.68 0.34 50x5.5 = 275 Scrap iron twenty 3.2 0.64 2.2 0.44 0.2 0.04 20x5.5 = 110 Steel scrap 1A fifteen 0.3 0,045 0.3 0,045 0,07 0.01 15.5x5.5 = 82.5 Steel scrap B10 3 sixteen 0.48 3x5.5 = 16.5 Total charge one hundred 2,615 1.12 0.87 550 Carbon stick (12%) 2,615x0,12 = 0.314 Silicon burnout (20%) 1.12x0.15 = 0.168 Chrome fume (20%) 0.87x0.20 = 0.174 The content in the mixture, taking into account fumes (burn) 2.93 0.95 0.69

Note:

1. In this calculation, the following chemical composition of the casting was adopted,%: С - 2.93, 8ί - 0.95, Сг - 0.698.

2 hours before the end of the smelting company in the cupola and to switch from white chrome cast iron to gray cast iron, the charge was adjusted to obtain C - 3.0-3.3% and 8ί - 1.4-1.7%, the remaining metal was poured into mixer, knocked out a cupola.

2 hours before the end of the company, the smelters replaced the steel alloy scrap B10 with steel scrap 1A in the daily bunker. The remainder of the metal drained into the mixer should be at least 2-3 buckets (1.2-1.8 tons).

On casting, models of gray iron castings were installed.

The first three cupolas were filled with the first three fillings using a mixture containing 60-80% pig iron and 40-20% return, FS45 ferrosilicon and FMN70 ferromanganese according to calculation. The calculation of the charge is given in table. 3.

- 4 018034

Table 3. Calculation of the charge for the transition from white chrome cast iron to gray

The name of the charge materials and the calculation of additives Number of mater, in charge, kg Content. % Amount in the metal plant, kg Corner ROD Cream NIY Margg neck IN material in the charge IN material in the charge In the material in the charge Pig iron L5 80 4.0 3.2 1,6 1.28 0.6 0.48 80x5.5 = 440 Gray Cast Iron Return twenty 3.4 0.68 2,4 0.48 0.6 0.12 20x5.5 = 110 Scrap pig-iron purchased Steel scrap - - - - - - Total charge one hundred - 3.88 - 1.76 - 0.60 550 Carbon stick (3%) - - 3.88 x 0.03 = 0.02 - - - - - Silicon burnout (15%) - - - - 1.76x0.15 = 0.264 - - - Manganese Fumes (20%) - - - - - - 0.6x0.20 = 0.12 - The content in the mixture, taking into account fumes (burn) 3.9 1,5 0.48 Preset content in castings 3.9 2.6 0.6 Must be introduced as ferroalloy 1D 0.12 Additive ferroalloys taking into account fumes (over 100%): ferrosilicon 45% (fumes 25%) 1.375x100 45 = = 3.0 Ι, ΐχΐ, ΐχ 0.25 = 1.375 3x5.5 = 16.5 kg fs75 Ferromanganese (ferrosilicon manganese) (30% waste)> 0.144x100 70 = = 0.2 1.121 + 0.12 x 0.2 = = 0.144 0.2x5.5 = 1.1 kg Mp70

Mold filling began only after feeding three buckets (1.8 t) of gray cast iron to the mixer. The mass of metal in the mixer will be about 3.5 tons.

Approximately the average chemical composition of diluted cast iron in the mixer, taking into account the addition of three buckets (1.8 t) of gray cast iron, is determined as follows: approximate chemical composition of the metal residue in the mixer, wt.%: C - 3.2, 8ί - 1.5, Cg - 0.28 (see table. 4)

- 5 018034

Table 4. Calculation of the mixture to adjust the chemical composition of cast iron in the cupola during the transition from white chrome cast iron to gray.

The name of the charge materials and the calculation of additives Number of mater, in charge, kg Content% Amount in the metal plant, kg The corner! eode Cream NIY Hrs > m IN material in the charge IN material in the charge IN material in the charge Pig iron L4 Cast Iron Return 40 3.15 1.26 1.3 0.52 0.582 0.2328 40x5.5 = 220 Scrap pig-iron purchased 60 3.2 1.92 2.2 1.32 0.2 0.12 60x5.5 = 330 Total in charge one hundred - 3.18 - 1.84 - 0.353 550 Carbon stick (3%) - - 3.18x0.03 = 0.09 - - - - - Silicon burnout (20%) - - - - 1.55x205 = 0.368 - - - Chrome fume (20%) - - - - - 0.353x0.20 = 0.07 The content in the mixture, taking into account fumes (burn) 3.2 1,5 0.283

approximate chemical composition of the additive in the mixer of three buckets of gray cast iron, wt.%: C - 3.9; 8ί - 2.6; MP - 0.6; Cr - 0.1 (see table. 3);

the average chemical composition of cast iron in the mixer after dilution, wt.%:

With _cf = 3x3.2 + 3x3.9 = 21.3: 6 = 3.55;

δίςρ = 3 x 1.5 + 3 x 2.6 = 12.3: 6 = 2.05;

Cg _cf = 3 x 0.28 + 3 x 0.1 = 1.14: 6 = 0.19

This ensures the production of chromium cast iron and a free transition from chromium cast iron to gray with the production of residual chromium in dilute cast iron 0.19%, which is quite acceptable. Further, melting is carried out according to the batches at SCh10 or SCh20 with a further decrease in the chromium content, if necessary and if this allows the presence of a low chromium content in cast iron scrap.

Information sources.

1. Patent VI No. 2113495 C1, publ. 06/20/1998.

2. Patent No. 10945 C1, publ. 05/07/2008.

3. Patent No. 10946 C1, publ. 05/07/2008.

Claims (4)

CLAIM 1. A method of producing white chromium cast iron with a predetermined high chromium content under continuous melting conditions in a duplex process of cast iron with various chromium contents, including melting the mixture in a cupola to produce molten cast iron, followed by accumulation and refinement of molten cast iron by chemical composition in a mixer, at the first stage, cast iron is smelted using a starting charge and added to the total volume of the mixer in the remainder of the cast iron in the mixer with a chromium content other than specified, and if necessary Accordingly, the composition of the cast iron is adjusted according to C, δί, Mn to produce white chromium cast iron with a given high chromium content, and the chromium content in the starting charge is selected in order to achieve a given value of chromium content when mixed in a predetermined proportion of molten cast iron obtained from the starting blend with the mixer with the remainder of cast iron, and in the second stage after the accumulation of the return of white chromium cast iron with a given high chromium content, the cast iron is smelted using a constant mixture, which is introduced Return it chromium white cast iron with high chromium content specify. 2. The method according to claim 1, characterized in that scrap B10 of corrosion-resistant and heat-resistant chromium steels with the content,%: Cr - 6-18, Τι - not more than 0.8, N1 - not more than 0.6, is introduced into the composition of the starting charge . 3. The method according to any one of claims 1 or 2, characterized in that as the starting mixture using a mixture of the following composition, wt.%: - 6 018034 pig iron L6 14-16 return fittings 64-66 steel scrap A1 14-16 steel scrap B10 4-6. 4. The method according to any one of claims 1 to 3, characterized in that as a constant charge using a mixture of the following composition, wt.%: pig iron L4 11-13 white cast iron return 49-51 pig-iron scrap 19-21 steel scrap 1A 14-16 steel scrap B10 2-4. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2